Misc: Django 5.2 update

[thmsrmbld]

Django 5.2 Compatibility Update

This PR updates the project to support Django 5.2 and makes several modernization improvements.

Changes

1. Added Django 5.2 compatibility
2. Deprecated support for Django versions before 4.2 (removing 3.2, 4.0, 4.1)
3. Updated tox configuration to test against supported Django versions
4. Ensured Django main branch is only tested on Python 3.12
5. Updated GitHub Actions workflow matrix to reflect Django version changes

Also: Addressed an issue where tests were failing in Django 5.2 due to a change in output handling. In previous Django versions, writelines() would implicitly add newlines between elements. But Django 5.2 aligns with Python's standard behavior where it doesn't. Fixed by explicitly adding newlines when outputting content in the print_contents() method of DiffCheckCommand, ensuring consistent behavior across all supported Django versions and keeping the test passing.

Tooling Improvements

1. Updated ruff commands to use modern ruff check syntax
2. Modernized ruff configuration in .ruff.toml to use new section-based format
3. Updated pre-commit configuration to add explicit ruff check hooks

Documentation

1. Updated README with compatibility information
2. Updated CHANGELOG to document version 0.4 changes
3. Bumped project version from 0.3 to 0.4 in pyproject.toml
4. Updated pyproject.toml classifiers to reflect supported Django versions

[thmsrmbld]

Addresses an issue where tests were failing in Django 5.2 due to a change in output handling. In previous Django versions, writelines() would implicitly add newlines between elements. But Django 5.2 aligns with Python's standard behavior where it doesn't. Fixed by explicitly adding newlines when outputting content in the print_contents() method of DiffCheckCommand, ensuring consistent behavior across all supported Django versions and keeping the test passing.